The present invention relates to a starting clutch, particularly for racing and sports vehicles, having clutch plates, of which at least one is non-rotatably coupled with a clutch cage of the starting clutch and at least one is non-rotatably coupled with a clutch hub of the starting clutch. A spring assembly composed of at least two diaphragm-spring-type spring elements presses the clutch plates together when the starting clutch is closed and permits a torque transfer from the clutch cage to the clutch hub and vice-versa. A starting clutch of the concerned type is known from German Patent Document DE 10 2006 012 809 A1.
Multi-plate clutches having a stack of plates consisting of several individual plates are generally used as starting clutches in racing and sports vehicles. In order to generate the contact pressure force between the plates that is necessary for torque to be transmitted, and to simultaneously achieve a compact construction of the clutch, very rigid clutch springs are required. Diaphragm springs, which are arranged in tandem in a stacked manner, are normally used as clutch springs.
In order to reach an optimal starting acceleration, an exact control of the clutch is necessary. Because of the rigid spring characteristic of the set of clutch springs, even small changes of the release position of the clutch will cause relatively large changes of the transferable torque. Especially if the clutch is opened too far, the desired driving power can not at all be transferred to the wheels. If, in contrast, the clutch is opened too little, there is the danger that too much power will be transferred to the driving wheels, which will then cause a spinning of the driving wheels and, as a result, an acceleration breakdown. In order to permit a more exact controlling or automatic controlling of the clutch, it was suggested in German Patent Document DE 10 2006 012 809 that the spring elements and the release element be constructed such that, starting from the closed condition of the clutch, when the clutch is gradually opened, at first only some of the existing spring elements are actuated by the release element and additional, or all, existing spring elements are actuated only after a further displacement path.
Inversely, during the closing of the clutch, at first only some of the spring elements are relieved or loaded, which permits the transfer of a partial torque of the maximally transferable torque. It is only after a further displacement path of the release element that additional or all spring elements of the clutch are relieved or loaded, which will then permit a transfer of the maximal possible clutch torque.
As a result of such a “stepped actuation” of the spring elements, a correspondingly stepped clutch characteristic is obtained (transferable torque as a function of the release path of the clutch), which has at least one plateau-type curve region extending along a predefined displacement path. In this curve region, the torque transferable by the clutch will be constant under mechanically ideal conditions or will change only relatively little along the displacement path.
However, interfering influences may occur in practice which may lead to considerable deviations from the theoretically given curve characteristic. Thus, friction parameters of the clutch may fluctuate from one actuating operation to another. Specifically, when actuating the set of clutch springs, a radial relative displacement of the mutually contacting diaphragm springs will occur to a certain extent as a result of the deformation of the diaphragm springs at the contact surfaces of the individual diaphragm springs. The frictional conditions occurring in this case depend on a plurality of parameters, such as the temperature, the lubrication, the dirt accumulation, etc. Particularly, the frictional relationships between the clutch spring (the so-called starting spring) that is first viewed from the stack of plates and the second clutch spring arranged behind the first clutch spring have a direct influence on the controllability or automatic controllability of a starting clutch.
It is an object of the invention to provide a starting clutch such that the controllability or automatic controllability of the clutch is improved during the start, i.e. during the closing of the clutch.
This and other objects are achieved by a starting clutch particularly for racing and sports vehicles, having clutch plates, of which at least one is non-rotatably coupled with a clutch cage of the starting clutch and at least one is non-rotatably coupled with a clutch hub of the starting clutch. The clutch cage can be flanged directly to the crankshaft of the engine, and the clutch hub can be connected to a transmission input shaft. Furthermore, a set of springs (spring assembly) is provided having at least two diaphragm-spring-type spring elements, which springs press the clutch plates together when the starting clutch is closed and permit a torque transfer from the clutch cage to the clutch hub and vice-versa. Advantageous developments and further developments of the invention are contained in the subclaims.
The invention is based on a recognition that the lower and the more constant the frictional relationships are between the first two spring elements—viewed from the clutch plates—the better the clutch can be controlled or automatically controlled. According to the invention, viewed from the clutch plates, the first or the second spring element has at least one elevation on its side facing the second or first spring element, respectively, which elevation presses against the respective second or first spring element when the starting clutch is closed.
In contrast to the state of the art, for example the clutch described in German Patent Document DE 10 2006 012 809 A1, the two first spring elements therefore no longer contact one another in a large-surface or full-surface manner, but at least at one first elevation. This reduces the friction between the two first spring elements. The frictional conditions between the two first spring elements thereby clearly become more constant; i.e. they will no longer vary as much as in the case of conventional starting clutches.
The spring element that is first or second viewed from the clutch plates preferably has at least a second elevation on its side facing the respective second or first spring element, which second elevation presses against the respective second or first spring element when the starting clutch is closed.
The first elevation and the second elevation have different distances from an axis of rotation of the starting clutch. By means of the mutually radially spaced elevations, a defined distance between the two first springs can be provided. The two elevations preferably have the same “height” in the longitudinal direction of the axis of rotation of the starting clutch, so that the two first springs will be parallel to one another when they are pressed against one another. As an alternative thereto, it may also be provided that the at least one, first and the at least one, second elevation have different heights, which implies that the diaphragm springs do not absolutely have to be parallel when they are pressed against one another.
According to a further development of the invention, the second elevation is located radially outside of the first elevation with respect to the axis of rotation of the starting clutch. Preferably, the elevations are provided on the side of the first spring element facing the second spring element.
The elevations may each have the shape of a closed “cutting-edge-type” ring. As an alternative, the at least one, first elevation and the at least one, second elevation can also be formed by several cutting-edge-type ring sections spaced apart from one another in the circumferential direction. Instead of ring sections, a plurality of “contact points” forming the elevations are also contemplated.
According to a further development of the invention, a ring-shaped pressure element is arranged between the first spring element viewed from the clutch plates and the first clutch plate. The pressure element may have the shape of a ring-shaped pressure plate. An area of highest surface pressure is situated between the first clutch plate and the pressure element or the pressure plate. The first elevation is preferably at essentially the same radial distance from the axis of rotation of the starting clutch as the region of the highest surface pressure. As a result, it is ensured that the contact pressure force transferred from the first spring element is optimally introduced into the pressure element or the pressure plate of the starting clutch. The surface pressure can correspondingly be reduced as a result of a plane contact.
According to a further development of the invention, the starting clutch has a release element which can be displaced along the axis of rotation of the clutch. By displacing the release element, the spring elements can be deformed such that the starting clutch is opened. In a manner similar to the manner of the starting clutch described in German Patent Document DE 10 2006 012 809 A1, the spring elements and the release element may be constructed such that, starting from a position in which the starting clutch is completely closed, during displacement of the release element, the latter at first actuates only some of the spring elements and actuates additional (or the remaining) existing spring elements only after a further displacement path.
According to a further development of the invention, the spring elements and the release element are constructed such that, starting from a position in which the starting clutch is completely closed, during displacement of the release element, the latter actuates only the second and possibly existing further spring elements and actuates the first spring element (starting spring) only after a further displacement path.
Furthermore, it may be provided that the first spring element has a larger inside diameter than the second spring element and the release element has at least two driving areas or driving sections.
It is explicitly pointed out that the entire disclosure content of German Patent Document DE 10 2006 012 809 A1 is expressly incorporated by reference herein. All characteristics, ideas or partial ideas explicitly or implicitly contained in German Patent Document DE 10 2006 012 809 A1 can therefore literally or analogously be applied herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.